US7867353B2 - Thermally and electrically conductive interface - Google Patents
Thermally and electrically conductive interface Download PDFInfo
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- US7867353B2 US7867353B2 US12/141,257 US14125708A US7867353B2 US 7867353 B2 US7867353 B2 US 7867353B2 US 14125708 A US14125708 A US 14125708A US 7867353 B2 US7867353 B2 US 7867353B2
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/20—Layered products comprising a layer of metal comprising aluminium or copper
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
- B32B27/26—Layered products comprising a layer of synthetic resin characterised by the use of special additives using curing agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/28—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
- B32B27/283—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42 comprising polysiloxanes
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/0058—Laminating printed circuit boards onto other substrates, e.g. metallic substrates
- H05K3/0061—Laminating printed circuit boards onto other substrates, e.g. metallic substrates onto a metallic substrate, e.g. a heat sink
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
- B32B2264/10—Inorganic particles
- B32B2264/105—Metal
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
- B32B2307/202—Conductive
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/30—Properties of the layers or laminate having particular thermal properties
- B32B2307/302—Conductive
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/30—Properties of the layers or laminate having particular thermal properties
- B32B2307/306—Resistant to heat
- B32B2307/3065—Flame resistant or retardant, fire resistant or retardant
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
- B32B2309/02—Temperature
- B32B2309/022—Temperature vs pressure profiles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2457/00—Electrical equipment
- B32B2457/08—PCBs, i.e. printed circuit boards
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
- B32B37/0007—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding involving treatment or provisions in order to avoid deformation or air inclusion, e.g. to improve surface quality
- B32B37/003—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding involving treatment or provisions in order to avoid deformation or air inclusion, e.g. to improve surface quality to avoid air inclusion
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
- F28F2013/005—Thermal joints
- F28F2013/006—Heat conductive materials
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/01—Dielectrics
- H05K2201/0137—Materials
- H05K2201/0162—Silicon containing polymer, e.g. silicone
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/01—Tools for processing; Objects used during processing
- H05K2203/0191—Using tape or non-metallic foil in a process, e.g. during filling of a hole with conductive paste
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/06—Lamination
- H05K2203/068—Features of the lamination press or of the lamination process, e.g. using special separator sheets
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/321—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by conductive adhesives
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/31504—Composite [nonstructural laminate]
- Y10T428/31652—Of asbestos
- Y10T428/31663—As siloxane, silicone or silane
Definitions
- the present invention relates to electrical interfacing in electronic devices and more specifically relates to using an interface material to bond a high or low frequency circuit board with a heat sink.
- PCB printed circuit board
- thermoset polymers such as epoxy resins. Once a thermoset polymer is cured, it is inflexible. Thus, a major drawback of interface materials based on thermoset polymers is their inability to expand or contract with changes in the surrounding temperature. Also, epoxy resins usually have a lower temperature stability (up to about 400 F) as compared to silicones that can be used up to about 550 F. As a result, high power PCBs based on thermoset interfaces can exhibit weakening or even delamination at the circuit/heat sink interface if the interface temperature exceeds about 400 F due to the high heat generated during the performance of high power electronic components that are assembled over the PCB. There is a need, therefore, for an advancement in the art of preparing electrically and thermally conductive interface materials and in manufacturing circuit board assemblies using the interface material.
- the present invention is directed to an electrically and thermally conductive interface material and its application in a circuit board assembly.
- An electrically and thermally conductive interface material (“interface”) is provided as a mixture of a silicone-based compound, metal flakes and/or granules, flame retardant and a curing catalyst.
- the interface material may be pre-formed into a film or pad aid each side of the film protected with removable release layers. Each side of the film may also include a coating of an adhesive material that aids in coupling the interface film with a metal surface.
- the interface material may alternatively be produced in a screen-printable paste. As such, a layer of the interface material paste may be screen-printed on the metal surface.
- the screen used for printing the paste on the metal surface can be either without any stencil pattern to allow the entire metal surface to be covered with the paste, or the screen can be mask patterned suitably to allow the paste applied in the corresponding pattern form on the metal surface.
- the interface material is sandwiched between a printed circuit board and a heat sink to form the circuit board assembly.
- the interface film can be precut (e.g., by using a stencil to obtain complex film shapes), properly aligned and sandwiched between a printed circuit board and heat sink to form the assembly.
- a multi-step press process for bonding the assembly is cured and a laminate formed.
- the multi-step process includes a first pressure treatment applied to the assembly at room temperature to increase surface contact and to remove air pockets, a second pressure treatment applied to the assembly at a high temperature to cure the interface and create a laminate; and a third pressure treatment applied to the assembly at room temperature to controllably return the assembly to room temperature.
- the bonding process may also include a priming function that prepares metal surfaces of the circuit board and heat sink for receiving the interface material.
- the interface material may also be applied in other formats, such as multi-layer circuits and to fill vias and channels in a circuit board. Further, the material may serve as an interface between a circuit component and a heat sink or other element.
- PCB printed circuit board
- Rf Radiofrequency
- FIG. 1 is a block diagram illustrating a circuit board assembly according to an exemplary embodiment.
- FIG. 2( a ) is a perspective view of an interface film in sheet form.
- FIG. 2( b ) is a perspective view of an interface film in roll form.
- FIG. 3 is a process flow of an exemplary embodiment of a manufacturing process of a circuit board assembly using pre-manufactured interface film.
- FIG. 4 is a process flow of an exemplary embodiment of a manufacturing process of a circuit board assembly using the interface material in a screen-printable paste form.
- FIG. 5 is a simplified schematic illustrating application of the interface material in a multilayer assembly.
- FIG. 1 is a diagram illustrating a circuit board assembly according to an exemplary embodiment.
- interface material 104 is sandwiched between a circuit board 102 and a heat sink 106 .
- excess heat generated by components mounted on the circuit board 102 may be shunted through interface material 104 to heat sink 106 .
- the interface material 104 is composed of a silicone-based dielectric and metal flakes or granules. When cured in a hot-press method, the interface material 104 also provides a mechanical bond to help secure the assembly. An organic catalyst is included to aid in the curing process. A flame retardant is added to suppress any burning tendency.
- the circuit board 102 is a printed (or printable) circuit board (PCB) on which electronic components may be mounted and may include a non-conducting substrate layer, such as a polytetrafluoroethylene (PTFE) and/or a fiberglass layer.
- the circuit board 102 preferably includes a metal base layer constructed of copper, for instance.
- the heat sink 106 is a metal element, such as an aluminum, brass or copper element configured to receive a heat transfer along a planar side (or a side contoured to any other non planer shape of the ground plane of the PCB) and to release excess heat from its other surfaces. While the heat-sink may be configured as a simple rectangular block, other configurations that may add additional surface area may be appropriate.
- the interface material 104 may be applied either as a screen-printable mixture or as a pre-formed laminate.
- the electrically and thermally conductive interface is composed of a mixture having silicone-based compound as the primary ingredient.
- the silicone-based compound may, for instance be a dimethyl polysiloxane (DMPS), commercially available from sources such as, Dow Corning, General Electric, Wackers, etc.
- DMPS dimethyl polysiloxane
- the silicone-based compound is easily obtainable and is more resistant to thermal shocks than other compounds such as an epoxy.
- the silicone based compound is present in the interface mixture at a concentration of about 40% to about 75% of silicone base, by weight based on the total weight of the interface material.
- Metal flakes and/or granules are included in the interface mixture to provide electrically and thermally conductive properties.
- the metal that may be used include silver, silver plated particles made up of other materials such as aluminum, etc.
- the currently preferred type is silver.
- the metal flakes and/or particles are about 100 to 300 micrometers (microns) in average diameter, and are present in the interface mixture at a concentration of about 20% to about 75%, preferably about 40% to about 75%, by weight (of metal) based on the total weight of the interface material.
- a curing catalyst is included in the interface mixture to promote and/or control the curing reaction.
- the curing catalyst may also serve as a hardener.
- the catalyst is present in the interface mixture at a concentration of about 0.1% to about 10% by weight based on the total weight of the interface material. As is understood by those skilled in the art, other materials are added to the interface mixture to provide various functionalities.
- the interface mixture may include one or more of the following components: up to about 5% by weight of the total weight of the interface mixture of benzoyl peroxide (as, e.g., a catalyst), up to about 5% by weight of the total weight of the interface mixture of PTFE, up to about 5% by weight based on the total weight of the interface mixture of 2,5-dimethylhexane, (which is the primary catalyst) and alumina trihydrate-platinum mixture as a fire retardant.
- the platinum-alumina trihydrate mixture may include between about 5.0% and 30.0%, by weight based on the total weight of the interface material.
- the platinum-alumina trihydrate mixture may include between about 0.1% and 2.0% platinum metal in alumina hydrate by weight based on the total weight of the platinum-alumina trihydrate mixture itself.
- the interface material is pre-manufactured (Pre-formed) film (laminate) that can be placed between the circuit board and the heat sink during assembly.
- Pre-formed film laminate
- FIG. 2( a ) provides an exemplary embodiment of the interface film in a sheet form.
- a protected interface film 200 includes the interface film 204 , a first release layer 202 protecting a first side of the interface film 204 and a second release layer (not shown) protecting a second side of the interface film 204 .
- An embodiment provides sheets sized at approximately 10′′ ⁇ 10′′ ⁇ 6 mil.
- Another embodiment provides sheets sized at approximately 18′′ ⁇ 12′′ ⁇ 5 mil.
- the release layers are removed to reveal the bare interface film 204 prior to placing the film within the circuit board assembly.
- FIG. 2( b ) provides an exemplary embodiment of the interface film in a roll form.
- a rolled protected interface film 250 includes the rolled interface film 256 , a first rolled release layer 252 protecting a first side of the rolled interface film 256 and a second release layer (not shown) protecting a second side of the rolled interface film 256 .
- a roll 258 allows a large amount of interface film to be stored without unduly bending or crimping the film. In operation, a portion of the rolled protected interface film 250 may be unrolled and cut according to manufacturing needs.
- the term “interface film” includes, but is not limited to, the sheet form and the rolled form.
- the mixture as described provides adhesive properties.
- an adhesive is included with the interface film to promote bonding with the metal surfaces of the heat sink and circuit board.
- the adhesive is added to the surface of both sides of the interface film prior to application of the release layer.
- the adhesive is added to the interface mixture prior to forming it as a film.
- FIG. 3 provides an exemplary process flow for manufacturing the circuit board assembly with the pre-manufactured interface film.
- the release layers are removed from each side of the interface film to expose the film.
- the interface film is then sandwiched between the circuit board and the heat sink.
- FIG. 3 shows function 302 occurring prior to function 304 , an embodiment provides that these steps are executed in an intertwined function.
- the intertwined function may include removing a first release layer from a first side of the interface film, then pressing the exposed side against a planar side of the heat sink. Once the interface film is (loosely) attached to the heat sink, the second release layer is removed to expose a second side of the interface film.
- the circuit board is then pressed against the second side to form the sandwich assembly shown in FIG. 1 .
- the intertwined function may be reversed so that the interface film is first attached to the circuit board and then attached to the heat sink. At this point, surfaces of the interface film are pliable and are configured to allow a high rate of surface contact.
- a room-temperature pressure treatment is applied to the assembly—pressing the heat sink toward the circuit board.
- this pressure treatment may be applied using a roller-assembly or other mechanisms.
- the room-temperature pressure treatment ideally works to (i) substantially remove any air-pockets that could reduce thermal conductivity and create ‘hot spots’ in the assembly and (ii) increase surface contact at the circuit board/film boundary as well as the heat sink/film boundary.
- a high-temperate pressure treatment is applied to the assembly—again pressing the heat sink toward the circuit board.
- the high-temperature press is intended to promote curing of the interface film as well as bonding of the interface film to the adjacent metal.
- the high-temperature bonding may occur at a temperature of approximately 330 degrees Fahrenheit and a pressure of approximately 480 PSI for approximately 20 minutes.
- these parameters may vary according to a number of factors, such as the thickness and composition of the interface layer and the particular requirements of any curing catalyst used, for instance.
- the high-temperature pressure treatment includes application of a temperature of at least 320 degrees Fahrenheit and pressure of at least 500 PSI for at least 20 minutes.
- a low-temperature pressure treatment is applied to the assembly—again pressing the heat sink toward the circuit board.
- the low-temperature pressure treatment is applied immediately following the high-temperature pressure treatment.
- the low-temperature may be room-temperature or another value at or below room temperature.
- the low-temperature is not a fixed temperature, but is a temperature that is reduced over time during the low-temperature pressure treatment.
- the silicone matrix forms cross-links that are hardened/cured.
- the low-temperature pressure treatment cools the interface down to room temperature under pressure without letting any air trap between the bonded layers. This may be necessary to avoid delamination of the bonded layers.
- circuit components may be assembled on the circuit board.
- the low-temperature first pressure treatment is accomplished at a pressure of approximately 75 PSI for approximately 1 minute.
- the circuit board has a metal base (such as a copper) that is attached directly to the interface film.
- a planar surface of the heat sink is the portion attached to the other side of the interface film.
- the metal surfaces Prior to attaching the circuit board and heat sink to the interface film, it may be appropriate to prepare the metal surfaces—thus helping to ensure better adhesion to the film.
- the preparation may include, for instance, degreasing, chemical cleaning, desmutting, physical roughening of the metal surface, cleaning the surface with alcohol and applying a thin coat of a primer material. This conditions the bondable metal surfaces for better adhesion with the silicone material.
- the outer surface of the aluminum surface may be given a surface finish of nickel and/or gold.
- anodizing the planar surface of the heat sink may serve to prepare the surface for binding with the interface film.
- the end result of the lamination process is that the circuit board assembly becomes a single element—the interface film bonded securely with both the metal bottom of the PCB and the planar surface of the heat sink. In some cases, excess interface material from an edge of the assembly may be trimmed.
- the thermally and electrically conductive mixture is provided in a screen-printable paste form.
- the screen printable form may provide a lower cost mechanism for creating a thermally and electrically conductive interface between the circuit board and the heat sink.
- FIG. 4 provides an exemplary process flow for manufacturing the circuit board assembly with the thermally and electrically conductive mixture in screen-printable paste form.
- the metal surfaces of the circuit board and heat sink are cleaned and primed. As described above, this may include degreasing, chemical cleaning, desmutting, and physical roughening of the metal surface and then cleaning the surface with alcohol and applying a thin coat of a primer material.
- an interface layer is screen printed onto one of the metal surfaces.
- either the metal base of the printed circuit board or the planar surface of the heat sink receives the screen printed layer.
- the screen printing may be adjusted to apply various layer thicknesses and pattern according to manufacturing specifications; in addition, the screen printing may be patterned to avoid artifacts in the circuit board such as vias and posts, for instance.
- the screen patterning technique includes stencil formation of required pattern on the screen.
- the screen-printing step is repeated until the interface layer is of a desired thickness.
- the screen printing can be performed manually or by a screen printing machine.
- the interface layer is then sandwiched between the circuit board and the heat sink to create the assembly.
- a room-temperature pressure treatment is applied to the assembly—pressing the heat sink toward the circuit board.
- this room-temperature pressure treatment may be applied using a roller-assembly or other mechanisms (as may the other pressure treatments).
- the room-temperature pressure treatment ideally works to (i) substantially remove any air-pockets that could reduce thermal conductivity and create ‘hot spots’ in the assembly and (ii) increase surface contact at the circuit board/film boundary as well as the heat sink/film boundary.
- the room temperature press may provide other benefits.
- a high-temperate pressure treatment is applied to the assembly—again pressing the heat sink toward the circuit board.
- the high-temperature press is intended to promote curing of the interface film as well as bonding of the interface film to the adjacent metal.
- the high-temperature bonding may be performed at a temperature of approximately 330 degrees Fahrenheit and a pressure of approximately 480 PSI for a duration of approximately 20 minutes.
- these parameters may vary according to a number of factors, such as the thickness and composition of the interface layer and the particular requirements of any curing catalyst used, for instance.
- the high-temperature pressure treatment includes application of a temperature of at least 320 degrees Fahrenheit and a pressure of at least 500 PSI for a duration of at least 20 minutes.
- a low-temperature pressure treatment is applied to the assembly—again pressing the heat sink towards the circuit board.
- the low-temperature pressure treatment is applied immediately following the high-temperature pressure treatment.
- the low-temperature pressure treatment is accomplished at approximately 200 PSI for approximately for 10 minutes or until the assembly is properly cooled.
- FIG. 5 shows a multilayer circuit board using the interface.
- a multilayer printed circuit board may have multiple layers 508 , 506 that are separated by a first interface 510 .
- Thermal vias 514 , 512 may thermally couple the first interface 510 with a second interface 504 .
- the second interface 504 being coupled with a heat sink 502 .
- the interface layers 504 , 510 may be either pre-manufactured interface films or screen-printed interface layers. Filling the vias 514 , 512 may be accomplished via screen-printing, injection, or other mechanical methods, for instance.
- FIG. 5 is a simplified embodiment.
- a working embodiment may include a greater number of thermal vias as well as more circuit board layers.
- the interface may also be useful to fill thermal channels that, for instance, shunt waste heat to an edge of the circuit board.
- the thermal channels may be filled in a similar fashion as the thermal vias.
- the interface may also be used to shunt waste heat to a heat sink.
- the thermally and electrically conductive material may be used to couple an electronic component directly to a heat sink.
- the interface may be used to couple a processor, a LED device, an electric motor, or a power source directly with a heat sink.
- Table 1 Typical data for a six mil thick silicone interface film is provided in Table 1.
- Table 1 The results shown in Table 1 are a summary of data obtained from test results performed on a preformed electrically and thermally conductive layer constructed in accordance with an exemplary embodiment.
- an interface film may be manufactured with any thickness ranging from 5 mil upwards According to a preferred embodiment, it is important to maintain a substantially uniform thickness across a manufactured film in order to ensure a strong bond with the circuit board and heat sink.
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Laminated Bodies (AREA)
- Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
- Cooling Or The Like Of Electrical Apparatus (AREA)
Abstract
Description
TABLE 1 | ||||
Test Method | Property | Value | ||
ASTM D3767 | Thickness | 6 mil. | ||
ASTM D412 | Tensile Strength | >200 PSI | ||
ASTM D2240 | Hardness (Shore A) | 80-90 | ||
ASTM D412 | Elongation | >200% | ||
Tear Strength | >60 PPI | |||
ASTM D5470 | Thermal Conductivity | 0.6 to 25.0 W/m-K | ||
MIL G 83528 | Electrical Resistivity | <0.0007 ohmcm | ||
Claims (7)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/141,257 US7867353B2 (en) | 2006-02-08 | 2008-06-18 | Thermally and electrically conductive interface |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11/349,842 US7527873B2 (en) | 2006-02-08 | 2006-02-08 | Thermally and electrically conductive interface |
US12/141,257 US7867353B2 (en) | 2006-02-08 | 2008-06-18 | Thermally and electrically conductive interface |
Related Parent Applications (1)
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11272610B1 (en) | 2020-08-28 | 2022-03-08 | Kioxia Corporation | Printed wiring board, memory system, and method for manufacturing printed wiring board |
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US20080251199A1 (en) | 2008-10-16 |
US20070184289A1 (en) | 2007-08-09 |
US7527873B2 (en) | 2009-05-05 |
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